Terrifying scene ahead of the Atlanta Hawks game on Monday night ... Bob Rathbun, the team's play-by-play announcer, suffered a frightening medical emergency while on air -- and needed to be rushed to the hospital.
Thankfully, however, the 68-year-old is now said to be doing better ... and is in "stable" condition.
Rathbun was previewing the Hawks' game against the Thunder for Bally Sports with Dominique Wilkins ... when he suddenly appeared to lose consciousness in his chair, and convulse uncontrollably.
WARNING -- THE VIDEO IS HARD TO WATCH.